A controller can provide a control signal to a converter, which converts an input voltage to an output voltage based upon the control signal. These kinds of controllers may utilize a pulse width modulation (PWM) signal as the control signal and are referred to as PWM controllers. In a relatively heavy load application, e.g., a high-end microprocessor or Graphics Processor Unit (GPU) which requires a high load current, e.g., more than 30 Amperes (A), a multi-phase controller is widely employed, where two or more phases are used by the controller to meet the load requirement. However, the conventional multi-phase controller tends to share the heavy load unevenly, due to an unbalanced condition among the multiple phases. As a result of the unbalanced condition, the phases with heavier loads relative to others will suffer thermal stress. Contributors to the unbalanced condition range from mismatches in the control timing and layout of the controllers among the multiple phases to process variations in similar blocks of the multiple phases.
Typically, current balancing circuits are employed in the multi-phase controllers to share the load current evenly among the multiple phases. For current balancing, an additional current sensor is used to detect a current through a respective phase. The sensed phase current is fed to a correction circuit which adjusts the duty cycle of the respective phase in response to the unbalanced condition. However, the mismatch among the current sensors would still affect the balancing among the multiple phases. Further, the additional current sensors and correction circuits will increase the system cost, lower efficiency, and increase the die area of the multi-phase controllers.